US health authorities on Friday declared a public health emergency in Puerto Rico due to the outbreak of Zika, which has now infected more than 10,000 people.
Zika is a mosquito-borne virus that can cause birth defects and is particularly dangerous for pregnant women.
A total of 1,035 pregnant women are among the 10,690 people who have been infected in the US territory of Puerto Rico in the past seven months, the island's health authorities said.
More than 1,900 cases of Zika were identified in the last week alone.
US Health and Human Services Secretary Sylvia Burwell declared "a public health emergency of national significance exists within the Commonwealth of Puerto Rico relating to pregnant women and children born to pregnant women with Zika."
Burwell said in a statement that the declaration would allow the United States to "provide additional support to the Puerto Rican government," but did not give further details.
Zika is primarily spread by mosquitoes, but can also be transmitted by sexual contact.
In four out of five cases, the virus causes no symptoms. Those who do feel sick have reported fever, rash, body aches and conjunctivitis, or pink eye.
Pregnant women are particularly urged to protect themselves against Zika because it raises the risk of birth defects including microcephaly, in which infants are born with small heads and malformed brains.
Zika has spread rapidly through Latin America and the Caribbean region since 2015.
The United States reported its first locally transmitted cases of Zika in Florida in July.